Biggest issue will be the low ceiling. If you can take out some ceiling tiles that would be great. Otherwise figure out things to hang/attach to the ceiling to break up the straight line reflection. Even some fabric loosely attached - make it look like a big circus tent.
For sound dampening you'd have to rebuild the building - split slab, non pierced walls, etc. Biggest thing you can do for you and the kids is to break up parallel surfaces. Straight line reflection is the enemy.